Sony FX 6 Quick Start Manual page 63

Exposure: Judging Image Noise
Be strict about your use of GAIN or ISO for optimal image quality.
You cannot judge image noise in the 720p LCD viewfinder. It is too small.
Image noise appears first in the shadow areas of an image.
If you are working in a studio consider attaching a large HDMI screen to
the camera to judge noise. This is critical when shooting green screen
backgrounds.